180 W. F. R. TVELDON. 



important papers by Braun^ and Mitsukuri/ the one dealing 

 with the development of the suprarenals in lizards, the other 

 in mammals. 



In lizards, Braun describes the cortical substance as arising 

 " as a thickening in the walls of the vena cava inferior." In 

 the earliest stage figured by him, a large mass of cortical 

 blastema is already established, as seen in PL 1, fig. 4 of his 

 paper. In this figure, as in ail the others given by Dr. 

 Braun, it is noticeable, as he himself says, that "the flattened, 

 nucleated endothelium (of the blood-vessel) is easily to be 

 distinguished " from the adjacent tissue, and that it shows no 

 sign of proliferation. It is therefore difficult to conclude from 

 this account that the suprarenals arise as appendages of the 

 blood-vessels themselves, Braun's observations throwing little 

 more light upon the real origin of the cortical substance than 

 did the earlier ones of Balfour. 



In the same way Mitsukuri, treating of mammals, finds the 

 first rudiment of the cortical substance in a little knot of 

 isolated mesoblast cells " on each side of and ventral to the 

 aorta, on the inner side of the Wolffian bodies, and dorsal to 

 the mesentery.'' 



Gottschau, in a later paper^ has described in mammals 

 phenomena nearly in accordance with those observed in lizards 

 by Braun, — emphasising more than Mitsukuri the connection 

 between the cortical substance and the adjacent blood-vessels. 



From none of these observations can "we learn anything of 

 the mode of origin of the blastema described, each author 

 taking up its history at a point when the cells composing it 

 have already lost any connection which they may primitively 

 have possessed with another embryonic organ. Janosik* has 

 attempted to trace the earlier history in mammals, and has 



I "Bau u. Entwick. d. Nebennieren bei Keptilien," Semper's 'Arbeiten,' 

 Bd. V. 



" " On the Development of the Suprarenal Bodies in Mammalia," ' Quart. 

 Jouru. Mic. Sci.,' 1882. 



•* ' Archiv. fiir Anat. u. Phys./ 1883. 



' 'Archiv fiir Mikr. Aiiat.,' 1883. 



